The invention concerns a tripod head with a universal joint, which has a ball joint swivelably and rotatably mounted in a bearing housing, wherein the universal joint is arranged between connecting points situated at oppositely facing ends of the tripod head, of which one is connected or connectable with a camera and the other with at least one tripod leg or similar mounting, wherein the ball joint, for restricting its swivelability to a swivelling motion about a swivelling axis running through the ball center point of the ball joint, is releasably connectable with an axial element.
Such a tripod head is known from U.S. Pat. No. 2,180,214 and from a prospectus of the firm EMO Optics, Wetzlar (1994). It has an axial element which, in the operating position, is inserted into a bore hole of the ball joint and with another portion penetrates an opening of the bearing housing. To release the swivelability of the ball joint in any desired direction, the axial element can be removed from the ball joint and the bearing housing. In the operating position, the axial element inserted into the bore hole of the ball joint forms a swivel bearing which fixes the swivelability and the rotatability of the ball joint relative to the bearing housing in a way such that the ball joint is still swivelable only about the swiveling axis, and is moreover blocked. It is thereby possible to incline a camera fastened to the tripod head in a swiveling plane running exactly perpendicular to the swiveling axis, without there existing the danger of the camera inadvertently tipping about the center of the ball joint transverse to the swiveling plane, or rotating about an axis running in the swiveling plane through the center of the ball joint.
The previously known tripod has the disadvantage that the axial element, when removed from the bore hole of the ball joint, can easily become lost, so that the swivelability of the ball joint can then no longer be fixed. A further disadvantage consists in that the insertion of the axial element into the ball joint requires a certain adroitness, since the opening situated in the bearing housing must be brought precisely into alignment before inserting the axial element in the bore hole of the ball joint. Moreover, the axial element must be positioned exactly axially in relation to the opening and the bore hole, so that the axial element can be inserted into the ball joint.
There thus exists the object of creating a tripod head of the type mentioned at the beginning in which the swivelability of the ball joint relative to the bearing housing is fixable in a simple way, such that the ball joint is only still swivelable about the swiveling axis and is furthermore fixed. In addition, the ball joint fixed in its swivelability should be re-releasable in a simple manner for swiveling or rotating it about any chosen axis running through the middle point of the ball joint, whereby the danger of losing the axial element is should be avoided.
The solution of this objective with a generic tripod head consists in that the axial element is arranged outside and adjacent to the ball joint and is pivotably mounted there on the bearing housing about the swiveling axis, that the axial element has on its end facing the ball joint at least one friction element for at least friction-locking connection with the ball joint, and in that a pressing device is provided by which the friction element is pressable on the ball joint.
Advantageously, the axial element is therefore connectable with the ball joint in a friction-locking manner, so that the axial element for fixing the swivelability of the ball joint is only pressed on the outer periphery of the ball joint and only needs to be withdrawn from this to release the swivelability of the ball joint. Moreover, it is even possible to connect the axial element with the ball joint in a friction-locking manner in various pivoting and/or swiveling positions of the ball joint in the bearing house, whereby the swivelability of the ball joint can be fixed about various swiveling axes. The axial element can be connected with the bearing housing in the fixed position or in the release position, whereby a loss of the axial element is avoided.
In an especially advantageous embodiment of the invention, the friction element has a concave friction surface adapted to the curvature of the ball joint. The friction element in the operating position then engages flatly on the outer circumference of the ball joint, which makes possible the transmission of correspondingly large forces of friction, and consequently a good restriction of the swivelability of the ball joint to a pivoting motion about a swiveling axis running through the center of the ball joint.
In an advantageous embodiment, it is provided that on both sides of a central plane of the ball joint at least one ring bearing is respectively arranged in the bearing housing, which has at least one respective sliding surface acting against a restoring force on the outer circumference of the ball joint, and that the friction element of the axial element engages on an outer peripheral area of the ball joint situated between the bearings. The ring bearings can thereby be pressed with a defined pressing force against the ball joint, so that the ring bearings exert a friction moment (torque) on the ball joint when swiveling or rotating the ball joint which, with a positioning of the camera with its center of gravity laterally spaced from a vertical through the center of the ball joint, wholly or partially compensates for a rotation moment (torque) acting on the ball joint by the weight of the camera. Advantageously, the friction moment transmitted from the ring bearings to the ball joint is largely independent of the pressing force by which the friction element is pressed on the ball joint. When the friction element in release position is pressed on the ball joint, a portion of the ring bearing situated on the same side of the ball joint as the friction element is namely respectively relieved, and at the same time, a portion of the ring bearing lying opposite this portion, arranged on the side of the ball joint facing away from the friction element, is more strongly loaded.
It is especially advantageous if at least one of the ring bearings is acted upon by an adjustable pressing force, and if an adjusting mechanism is preferably provided for this, which has within its transmission path at least one spring elastic element as well as at least one impinging piece having an inclined surface movable by means of a manual activation element. The friction moment of the ball joint can then be adapted to the respective weight of the camera, whereby this friction moment is largely independent of whether the friction element is connected in a friction-locking manner with the ball joint or is loosened from this.
It is provided in a preferred embodiment of the invention that the pressing device for the axial element has an adjusting element movable approximately radially to the center of the ball joint, and that the adjusting element is braced on the axial element through a pressure bearing, in particular having a pressure ball. A simply constructed point bearing thereby results, which makes possible a largely friction-free transmission of pressing force from the adjusting element to the axial element rotatable relative thereto about the swiveling axis, when the ball joint is swivelled in the bearing housing.
An especially simply constructed pressing device, by which a comparatively large pressing forces can be applied and transmitted to the friction element, can be achieved by the adjusting element having a screw thread arranged preferably concentrically to the swiveling axis of the ball joint, which is screwable together with a matching thread of the bearing housing for a separable connection of the axial element with the ball joint.
It is advantageous if the adjusting element has an inner cavity in which the axial element is rotatably mounted about the swiveling axis of the ball joint. The axial element is then arranged partially in the interior of the adjusting element, which makes possible a particularly compactly constructed mounting.
A preferred and especially advantageous embodiment provides that the friction element is made of rubber and the ball joint of metal, especially of anodized aluminum. Experiments have shown that with a friction element of rubber, an especially good friction-locking connection between the axial element and the ball joint is possible. Due to the elasticity of the material of the friction element, positional changes of the ball joint in relation to the friction element can be balanced out by swiveling the ball joint in the bearing housing, so that the friction element is at all times pressed against the ball joint, independently of the respective swiveling position of the ball joint, with a sufficient press-on force.
In an especially advantageous embodiment of the invention, it is provided that the bearing housing has an opening from which the ball joint partially protrudes, that on the portion of the ball joint protruding from the opening a shaft element connectable with the camera is arranged, and that the edge area of the bearing housing surrounding the opening has at least one slot into which the shaft element is partially swivelable and is preferably positionable such that the connecting line between the connection point for the mounting and the center of the ball joint, on the one hand, and the connecting line between the connection point for the camera and the center of the ball joint, on the other hand, are arranged at approximately right angles to each other. Moreover, it is even possible that the dimension of the slot oriented in the peripheral direction of the edge area surrounding the opening is adapted to the cross sectional dimension of the shaft element, and that when the shaft element is swivelled into the slot, the connecting line between the connecting point for the camera and the center of the ball joint runs at right angles to the swiveling axis of the axial element. Consequently, the ball joint, by swiveling the shaft element into the slot, can be brought into a defined position to the swiveling axis, in which the connecting line between the connection point for the camera and the center of the ball joint runs at right angles to the swiveling axis of the axial element. In this position the axial element can be pressed in a friction-locking manner onto the ball joint, so that the camera then moves in a plane when the ball joint swivels about the swiveling axis, whereby a tumbling motion of the camera is avoided.
It is advantageous if the tripod head has a rotation joint arranged preferably between the ball joint and the tripod connection point, by which the tripod head end having the tripod connection point is rotatable relative to the tripod end having the camera connection point, and if the rotation axis of the rotation joint is arranged at right angles to the swiveling axis and runs preferably through the center of the ball joint. The camera can then, for example, be rotated or swivelled in a horizontal plane around the axis of rotation of the rotation joint for photographing or filming a panorama.
Expediently, the tripod head has a setting device for fixing the ball joint, which has a clamping element clampable with the ball joint. The ball joint can then be locked in the bearing housing in all swiveling or rotation directions.
Expediently, the tripod head has at least one manual activation element which, relative to the bearing housing, is displaceable along a displacement axis, and is optionally rotatable about this, wherein the manual activation element has at least one protruding, shearable projection on its outer circumference, wherein the manual activation element engages with a portion having the projection into the interior of a holding sleeve connecting with the bearing housing extending in the direction of the displacement axis, and wherein the holding sleeve has at least one catch, preferably constructed as a collar, against which the projection is positionable by displacing the manual activation element along the displacement axis. The catch has a lead-in slope on its side facing away from the projection, when the manual activation element is in operating position, and a catching surface on the side facing the projection which is arranged at a steeper angle relative to the displacement axis than the lead-in slope.
The manual activation element can then be moved in the displacement direction to activate an equipment function of the tripod head, wherein the catch area of the catch limits the displacement path of the manual activation element in the pull off direction, so that this cannot be inadvertently pulled off of the holding sleeve. If the manual activation element is ever damaged, which can, for example, take place in connection with careless manipulation with a tripod having a tripod head, the manual activation element can be removed by applying a relatively large tractive force in the pull off direction. In this process the projection of the manual activation element shears off there on the catching surface of the catch. A new manual activation element can then be inserted into the holding collar, wherein upon insertion of the manual activation element its projection slides along on the lead-in slope inclined in the inlet direction, without being sheared off. The projection is preferably made of a more pliable material than the actual manual activation element, for example of rubber.
In an especially economically manufacturable manual activation element, the projection of the manual activation element is formed by an O ring inserted into a recess, preferably constructed as an annular groove.